This is the moment two lucky American tourists had the closest of encounters with some grey whales in Mexico.

The footage, captured on March 21, shows the massive mammals breaching the surface right next to the tourists' boat - and seemingly checking out the occupants.

''Grey whales have come to Mexico's Baja California for centuries to mate, calve, and relax before heading north to their Arctic feeding grounds,'' the filmer later wrote online.

''Seeing the whales blowing, sounding, mating, and calving in their natural habitat is an awesome and inspiring experience.''